Towards being genuinely smart : ‘isothermally-responsive’ polymers as versatile, programmable scaffolds for biologically-adaptable materials

Responsive polymers have found diverse application across polymer, biomaterials, medical, sensing and engineering fields. Despite many years of study, this has focussed mainly on those polymers which undergo thermally-induced changes – either a lower or upper critical solution temperature. To rival the adaptability of Nature's macromolecules, polymers must respond in a ‘smarter’ way to other triggers such as enzymes, biochemical gradients, ion concentration or metabolites, to name a few. Here we review the concept of ‘isothermal’ responses where core thermoresponsive polymers are chemically engineered such that they undergo their useful response (such as coil-globule transition, cell uptake or cargo release) but at constant temperature. This is achieved by consideration of their phase diagram where solubility can be changed by small structural changes to the end-group, side-chain/substituents or through main chain modification/binding. The current state-of-the-art is summarised here

Inferring Kangaroo Phylogeny from Incongruent Nuclear and Mitochondrial Genes

The marsupial genus Macropus includes three subgenera, the familiar large grazing kangaroos and wallaroos of M. (Macropus) and M. (Osphranter), as well as the smaller mixed grazing/browsing wallabies of M. (Notamacropus). A recent study of five concatenated nuclear genes recommended subsuming the predominantly browsing Wallabia bicolor (swamp wallaby) into Macropus. To further examine this proposal we sequenced partial mitochondrial genomes for kangaroos and wallabies. These sequences strongly favour the morphological placement of W. bicolor as sister to Macropus, although place M. irma (black-gloved wallaby) within M. (Osphranter) rather than as expected, with M. (Notamacropus). Species tree estimation from separately analysed mitochondrial and nuclear genes favours retaining Macropus and Wallabia as separate genera. A simulation study finds that incomplete lineage sorting among nuclear genes is a plausible explanation for incongruence with the mitochondrial placement of W. bicolor, while mitochondrial introgression from a wallaroo into M. irma is the deepest such event identified in marsupials. Similar such coalescent simulations for interpreting gene tree conflicts will increase in both relevance and statistical power as species-level phylogenetics enters the genomic age. Ecological considerations in turn, hint at a role for selection in accelerating the fixation of introgressed or incompletely sorted loci. More generally the inclusion of the mitochondrial sequences substantially enhanced phylogenetic resolution. However, we caution that the evolutionary dynamics that enhance mitochondria as speciation indicators in the presence of incomplete lineage sorting may also render them especially susceptible to introgression.This work has been supported by Australian Research Council grants to MJP (DP07745015) and MB (FT0991741). The website for the funder is www.arc.gov.au. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Activation of ice recrystallization inhibition activity of poly(vinyl alcohol) using a supramolecular trigger

Antifreeze (glyco)proteins (AF(G)Ps) have potent ice recrystallisation inhibition (IRI) activity – a desirable phenomenon in applications such as cryopreservation, frozen food and more. In Nature AF(G)P activity is regulated by protein expression levels in response to an environmental stimulus; temperature. However, this level of regulation is not possible in synthetic systems. Here, a synthetic macromolecular mimic is introduced, using supramolecular assembly to regulate activity. Catechol-terminated poly(vinyl alcohol) was synthesised by RAFT polymerization. Upon addition of Fe3+, larger supramolecular star polymers form by assembly with two or three catechols. This increase in molecular weight effectively ‘switches on’ the IRI activity and is the first example of external control over the function of AFP mimetics. This provides a simple but elegant solution to the challenge of external control of AFP-mimetic function

TPCK/TPACK Research and Development: Past, Present, and Future Directions

Scholarship addressing technological pedagogical content knowledge (TPCK or TPACK) has examined how to develop, apply, and assess it in diverse educational settings and content areas. During the last 12 years, multiple ways to understand this knowledge and support its development have emerged, generating approximately 1,200 publications that utilise the construct, impacting the practice of postsecondary faculty, administrators, and others invested in meaningful educational uses of technology. Perhaps inevitably, TPACK’s enthusiastic reception and rapid dissemination have generated multiple points of divergence, which in turn need further study; especially the construct\u27s accurate measurement and validation; how to assist preservice and in-service teachers\u27 TPACK development; contextual influences upon teachers\u27 TPACK; and the relationship of TPACK-based knowledge to teachers\u27 decision-making and action. Given the widespread diffusion of TPACK, research focusing on these and related issues will help to determine the direction of future postsecondary learning and teaching with technologies. Therefore, this special issue of AJET addresses future directions in TPCK/TPACK research and development

Co-operative transitions of responsive-polymer coated gold nanoparticles ; precision tuning and direct evidence for co-operative aggregation

Responsive polymers and polymer-coated nanoparticles have many potential bio-applications with the crucial parameter being the exact temperature where the transition occurs. Chemical modification of hydrophobic/hydrophilic or ligand binding sites has been widely explored as a tool for controlling this transition, but requires the synthesis of many different components to achieve precise control. This study reports an extensive investigation into the use of blending (i.e. mixing) as a powerful tool to modulate the transition temperature of poly(N-isopropylacrylamide) (PNIPAM) coated gold nanoparticles. By simply mixing two nanoparticles of different compositions, precise control over the transition temperature can be imposed. This was shown to be flexible to all possible mixing parameters (different polymers on different particles, different polymers on same particles and different sized particles with identical/different polymers). Evidence of the co-operative aggregation of differently sized nanoparticles (with different cloud points) is shown using transmission electron microscopy; particles with higher cloud points aggregate with those with lower cloud points with homo-aggregates not seen, demonstrating the co-operative behaviour. These interactions, and the opportunities for transition tuning will have implications in the rational design of responsive biomaterials

Adaptive foveated single-pixel imaging with dynamic super-sampling

As an alternative to conventional multi-pixel cameras, single-pixel cameras enable images to be recorded using a single detector that measures the correlations between the scene and a set of patterns. However, to fully sample a scene in this way requires at least the same number of correlation measurements as there are pixels in the reconstructed image. Therefore single-pixel imaging systems typically exhibit low frame-rates. To mitigate this, a range of compressive sensing techniques have been developed which rely on a priori knowledge of the scene to reconstruct images from an under-sampled set of measurements. In this work we take a different approach and adopt a strategy inspired by the foveated vision systems found in the animal kingdom - a framework that exploits the spatio-temporal redundancy present in many dynamic scenes. In our single-pixel imaging system a high-resolution foveal region follows motion within the scene, but unlike a simple zoom, every frame delivers new spatial information from across the entire field-of-view. Using this approach we demonstrate a four-fold reduction in the time taken to record the detail of rapidly evolving features, whilst simultaneously accumulating detail of more slowly evolving regions over several consecutive frames. This tiered super-sampling technique enables the reconstruction of video streams in which both the resolution and the effective exposure-time spatially vary and adapt dynamically in response to the evolution of the scene. The methods described here can complement existing compressive sensing approaches and may be applied to enhance a variety of computational imagers that rely on sequential correlation measurements.Comment: 13 pages, 5 figure

Enzymatically-triggered, isothermally responsive polymers: re-programming poly(oligoethylene glycols) to respond to phosphatase

Polymers which can respond to externally applied stimuli have found much application in the biomedical field due to their (reversible) coil–globule transitions. Polymers displaying a lower critical solution temperature are the most commonly used, but for blood-borne (i.e., soluble) biomedical applications the application of heat is not always possible, nor practical. Here we report the design and synthesis of poly(oligoethylene glycol methacrylate)-based polymers whose cloud points are easily varied by alkaline phosphatase-mediated dephosphorylation. By fine-tuning the density of phosphate groups on the backbone, it was possible to induce an isothermal transition: A change in solubility triggered by removal of a small number of phosphate esters from the side chains activating the LCST-type response. As there was no temperature change involved, this serves as a model of a cell-instructed polymer response. Finally, it was found that both polymers were non cytotoxic against MCF-7 cells (at 1 mg·mL–1), which confirms promise for biomedical applications

A review of 71 cases of infected total knee arthroplasty: mid-term to long-term follow-up

Departamentul de Chirurgie Ortopedică și Reabilitare, Universitatea Tech din Texas, Centrul de Știinţe ale Sănătaţii, Școala de Medicină Paul L. Foster, El Paso, Texas, Statele Unite ale Americii, Departamentul de Chirurgie Ortopedică, Spitalul General Buffalo, Universitatea de Stat din New York, Buffalo, New York, Statele Unite ale Americii, Departamentul de Chirurgie Ortopedică a Universităţii Harvard, Spitalul General Massachusetts, Boston, Statele Unite ale AmericiiIntroducere. În cadrul acestui studiu au fost evaluate caracteristici și rezultate la termen mediu și lung ale cazurilor de artroplastie totală de genunchi (ATG) și ale infecţiilor asociate cu acestea, care au fost tratate prin diferite metode. Material și metode. Studiul retrospectiv reflectă rezultatele a 71 de cazuri de ATG, infectate și tratate în perioada august 1993 – august 2005. Datele colectate includ înregistrări medicale cu privire la sexe, clasificarea infecţiilor periprotetice (IPP), comorbiditatea pacienţilor, criteriile de diagnostic ale IPP, rezultatele microbiologice și histopatologice, tratamentele chirurgicale și antimicrobiene, modalitaţile de tratament, complicaţiile, consecinţele, precum și rezultatele tratamentului. Nivelul de evidenţă: nivel terapeutic III. Rezultate. Vârsta medie a pacienţilor a constituit 70 de ani (extreme, 43–88 de ani). Mediana duratei de supraveghere – 10,8 ani (extreme, 5 – 20 de ani). Treizeci și trei (46,5%) de pacienţi au prezentat multipli factori de risc pentru IPP. Principalii patogeni izolaţi au fost stafilococii coagulazo-negativi – 26 (37%), Staphylococcus aureus – 16 (22,4%). Metodele de tratament ale ATG infectate au fost: înlocuirea în două etape – 59 (83%) de cazuri, debridare și retenţie – 5 (7,2%) cazuri, artrodeza – 5 (7,2%) cazuri, excizie-artroplastie – 2 (2,8%) cazuri. La sfârșitul perioadei de supraveghere, 17 genunchi (24%) au suportat intervenţie repetată, dintre care 10 (14%) – îndepărtarea componentelor din cauza reinfectării. Doi genunchi s-au reinfectat de 3 ori, trei genunchi – de două ori. Prima reintervenţie după reinfectare a fost efectuată după 1,2 ani (mediana), cu extreme cuprinse între 0,04 și 2,5 ani. Analiza curbelor Kaplan-Meier „de supravieţuire” a constatat că la 5 ani fără reintervenţie au ajuns 90,5% (95% CI între 85,3% și 96,1%) dintre pacienţi, iar la 10 ani – 82% (95% CI între 70,3% și 94,5%). Scorurile Asociaţiei Genunchiului (engl. Knee Society score): scorurile de durere, scorurile funcţionale, amplituda mișcării (engl. range of motion, ROM) – îmbunătăţite. Concluzii. Tratamentul ATG infectate este o sarcină dificilă, cu rezultate nesatisfăcătoare la termen mediu și lung. Aproximativ fiecare al patrulea pacient a necesitat o reintervenţie, iar 14% dintre pacienţi s-au reinfectat în primii 2,5 ani. Jumă- tate dintre pacienţii cu reinfecţie a ATG s-au reinfectat din nou. În majoritatea cazurilor, pacienţii s-au reinfectat cu același microorganism, dar mai virulent. Tratamentul unei ATG infectate ar putea fi ales în funcţie de tipul de infecţie (acută sau cronică), durata ei, stabilitatea implantului, specia agentului patogen, calitatea și integritatea osului și ţesutului moale.Introduction. In the present study, the characteristics and mid-term to long-term outcomes of total knee arthroplasty (TKA) associated infections treated with different types of approaches were evaluated. Material and methods. A retrospective study of the results of 71 infected TKA treated between August 1993 and August 2005. The data included medical records, gender, periprosthetic infection (PPI) classification, patients’ comorbidities, PPI diagnostic criteria, microbiology and histopathology results, surgical and antimicrobial therapy, treatment modality, complications, follow up, and treatment results. Level of Evidence: Therapeutic Level III. Results. Median age was 70 years (range, 43–88). Median follow-up 10.8 years (range, 5–20). Thirty-three patients had multiple risk-factors for PPI. The main pathogens isolated were Coagulase-negative staphylococci 26 (37%), Staphylococcus aureus 16 (22.4%). The treatment methods of TKA infection were two-stage exchange in 59 (83%), debridement and retention – 5 (7.2%), arthrodesis – 5 (7.2%), excision arthroplasty 2 (2.8%). At final follow up, 17 knees (24%) had required reoperation: 10 knees (14%) – component removal for reinfection. Two knees were reinfected 3 times, three knees – two times. The median time to first reoperation for reinfection was 1.2 years (range, 0.04–2.5 years). By Kaplan-Meier survival analysis the estimated survivals free of reoperation for infection were 90.5% (95% confidence intervals, 85.3% to 96.1%) at 5 years and 82% (95% confidence intervals, 70.3% to 94.5%) at 10 years. The Knee Society scores: Pain scores, Functional scores, ROM improved. Conclusions. TKA infections treatment is a difficult task leading to a high rate of unsatisfactory mid-term and longterm results. About one forth of patient require reoperation, 14% become reinfected in first 2.5 years. Half of reinfected patients get reinfected repeatedly. In most cases patients are reinfected with the same microorganism but more virulent. TKA infection treatment option should be chosen according to the type of infection (acute or chronic), the duration of infection, the stability of the implant, the type of microorganism causing infection, bone quality and integrity, and the quality of the soft-tissue